J Neurogastroenterol Motil 2018; 24(4): 570-576  https://doi.org/10.5056/jnm18010
Improving High-resolution Impedance Manometry Using Novel Viscous and Super-viscous Substrates in the Supine and Upright Positions: A Pilot Study
Uni Wong,1,2 Erik B Person,1,2 Donald O Castell,3 Erik von Rosenvinge,1,2 Jean-Pierre Raufman,1,2 and Guofeng Xie1,2*
1Division of Gastroenterology and Hepatology, University of Maryland School of Medicine, Baltimore, MD, USA; 2Veterans Affairs Maryland Health Care System, Baltimore, MD, USA; and 3Division of Gastroenterology and Hepatology, Medical University of South Carolina College of Medicine, Charleston, SC, USA
Correspondence to: Guofeng Xie, MBBS, PhD
Division of Gastroenterology and Hepatology, University of Maryland School of Medicine, 22 South Greene St., Baltimore, MD 21201, USA
Tel: +1-410-706-5962, Fax: +1-410-328-8315, E-mail: gxie@som.umaryland.edu
Uni Wong and Erik B Person contributed to this work equally.
Received: January 10, 2018; Revised: April 27, 2018; Accepted: June 4, 2018; Published online: October 1, 2018.
© The Korean Society of Neurogastroenterology and Motility. All rights reserved.

cc This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Swallows with viscous or solid boluses in different body positions alter esophageal manometry patterns. Limitations of previous studies include lack of standardized viscous substrates and the need for chewing prior to swallowing solid boluses. We hypothesize that high-resolution impedance manometry (HRiM) using standardized viscous and super-viscous swallows in supine and upright positions improves sensitivity for detecting esophageal motility abnormalities when compared with traditional saline swallows. To establish normative values for these novel substrates, we recruited healthy volunteers and performed HRiM.
Standardized viscous and super-viscous substrates were prepared using “Thick-It” food thickener and a rotational viscometer. All swallows were administered in 5-mL increments in both supine and upright positions. HRiM metrics and impedance (bolus transit) were calculated. We used a paired two-tailed t test to compare all metrics by position and substrate.
The 5-g, 7-g, and 10-g substrates measured 5000, 36 200, and 64 700 mPa∙sec, respectively. In 18 volunteers, we observed that the integrated relaxation pressure was lower when upright than when supine for all substrates (P < 0.01). The 10-g substrate significantly increased integrated relaxation pressure when compared to saline in the supine position (P < 0.01). Substrates and positions also affected distal contractile integral, distal latency, and impedance values.
We examined HRiM values using novel standardized viscous and super-viscous substrates in healthy subjects for both supine and upright positions. We found that viscosity and position affected HRiM Chicago metrics and have potential to increase the sensitivity of esophageal manometry.
Keywords: Esophageal motility disorders; Manometry; Viscous substrates
Fig. 1. Examples of high-resolution impedance manometry studies using novel viscous and super-viscous solutions. Impedance and high-resolution manometry plots are shown in the top and bottom panels, respectively. (A) 5-g “Thick-It” solution. (B) 7-g “Thick-It” solution. (C) 10-g “Thick-It” solution.

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